Consider a load-independent station fed with two Poisson arrival streams. Both types of customers have the same exponentially distributed service times. The server gives preemptive priority to class 1...

Consider a load-independent station fed with two Poisson arrival streams. Both types of customers have the same exponentially distributed service times. The server gives preemptive priority to class 1 customers over class 2 customers. Using the notion of quasi reversibility, show that the class 1 departure stream and the overall departure stream are Poisson, but the class 2 departure stream is not!